M lenses on APC Camera

I know with Nikon putting a FX lens on a DX body changes the focal length by the crop factor of the body. So a 50mm becomes an 75mm or something like that. I expect the same thing happens when you put an M lens on the T. Or is there something about the registration distance or a lens in the M adaptor which makes this not happen. It doesn't seem to be mentioned in any of the reviews that I've seen where they use an M lens.